Under searing heat conditions, people are prone to sunstrokes, i.e. to suffer from an incapacitating health condition attributable to intense heat and sunray levels. Even if sunstroke is not reached, various intermediate conditions can be observed: loss of concentration, irritability, decreased physical performance output (for sportsmen), and generally speaking, a certain level of discomfort. This situation is compounded by the fact that the hat a person wears, which is effective in shielding the head from sun burns, may on the other hand generate increased perspiration and thus incomfort, leading undesirably to its removal by that person.
The existing cold-storing devices, such as the so-called ice-packs, are useful in keeping foodstuff cool. But when it comes to applying those devices against a person's body, the direct or indirect contact generates a thermal shock which may freeze the corresponding skin portion of this person. Accordingly, by trying to shield the person from extreme heat, we impose upon him exactly the inverse situation, namely, submitting him to extreme cold at a localized area--an unsatisfactory solution.
A typical illustration of such prior art devices is disclosed in U.S. Pat. No. 3,090,045 issued May 21, 1963 to Mr. Howard Lee HURST. In this patent, a flexible bag 1 is to be mounted either inside (FIG. 1) or in overhanging fashion over (FIG. 6) a conventional cap or hat 18. Bag 1 encloses a plurality of ice cubes 14. It is understood that in the embodiment of FIG. 1, the bag 1 abuts directly against the scalp of the person; while in the embodiment of FIG. 6, the fabric of the hat 18 is sandwiched between the bag 1 and the head of the person. However, in both cases, head cooling is achieved thanks to thermal conduction, i.e. transfer of cold by direct or indirect contact with the head. We have already explained why such an arrangement is unsatisfactory: a thermal shock may occur because of the conductive nature of the thermal transfer.
Another example of prior art head cooling devices includes the one disclosed in U.S. Pat. No. 5,054,122 issued Oct. 8, 1991 to the Taiwanese Cheng-Hsien SHER. A conical hat 1 is provided, with an annular channel member 10 installed at an intermediate portion thereof. This channel member 10 supports cooling elements 2 (heat absorbing chemicals). The cold air thus released by the cooling elements is allowed to circulate inside the hat through a plurality of vent holes 31, made on an inner ventilation socket 3, to cool the head. In this case, head cooling operates under convection forces, i.e. via the air circulation induced by variation in air density associated with a thermal gradient. Clearly, and as is apparent from FIG. 6, the inner ventilation socket substantially engage directly against the head, so that only a small area of the head will be immediately cooled, the remainder of the head (and of the person's body) being cooled through endogenous (vascular) thermoregulation. Obviously, such an arrangement cannot be adapted to safety helmets, farmer's hats, or the like. The cold-releasing chemical agents 2 inside the channel member 10 could possibly pose a safety threat, should they accidentally leak from their cells and come in direct engagement with the head (the head being the most fragile part of the body, which is why through the million years of human evolution, the head has moved farthest away from the dangerous ground level). Finally, some conduction-type thermal transfer cannot be excluded, since the layers 10, 2 and 3 are in direct engagement with one another, so that the scalp may again be undesirably subjected to a thus induced thermal shock via indirect engagement with the cold releasing cells 2.